In the world of computer software, programming languages are either dynamically typed or statically typed. In dynamically typed languages, a variable can be used without specifying what data type it represents (i.e. without declaring a data type). At runtime, the system determines what data type the variable represents, and treats it accordingly. Python, PHP, and VB Script are examples of dynamically typed languages. In statically typed languages, variables must be declared before they are used. For example, if you want to use a variable called Counter to track the number of times a certain program has executed, you would have to declare the Counter variable as a particular numeric type, such as an integer, before using the variable in an operation. With statically typed languages, the data type of each variable is known at compile time. Some examples of statically typed languages are Java, C++, and C.
One common problem is the difficulty in writing code that could target multiple different numeric types rather than being specific to just one. For example, you might want to write a routine that adds the elements of an array of numeric types. Conventional techniques require duplicating code for each type supported. Generics allow a single API signature to potentially work on a number of types, but without an interface to allow the arithmetic operations, it is not possible to do the summation.
The advantage of a generic interface over a non-generic one is that it allows routines or classes that use the interface to be strongly typed, so that for example, if the result of a generic math algorithm is assigned to the wrong data type, an error is generated at compile time. Statically typed languages treat each numeric type as very different entities, thereby making even basic math among numeric types sometimes difficult.